Dodge RAM TRUCK 1500 1995 Service Manual page 229

B R DISC BRAKES I -17
CONTROL
FRONT HOSE
AND TUBE
ASSEMBLY J9405-51
Fig. 30 Front Brake Hose Routing (4-Wheel Drive)
(5) Fill and bleed brake system. Refer to procedure
in appropriate antilock brake section.
(6) Install wheel and tire assemblies and lower ve­
hicle.
DISC BRAKE ROTOR INSPECTION AND SERVICE
Rotor condition and tolerances can be checked with
the rotor mounted in a brake lathe, or on the axle. If
the rotor is checked on the axle, be sure wheel bear­
ing end play is reduced to zero before measuring lat­
eral runout.
The rotor braking surfaces should not be machined
unless actually necessary. Light surface rust and
scale can be removed in a lathe equipped with dual
sanding discs.
Worn, or scored rotor surfaces can be restored by
machining in a disc brake lathe but only if surface
scoring and wear are light.
The rotor should be replaced if:
• severely scored
• tapered
• has hard spots
• cracked
• warped
• too thin
• machining would take rotor below minimum thick­
ness
CHECKING ROTOR MINIMUM THICKNESS
Measure rotor thickness at the center of the brake-
shoe contact surface. Replace the rotor if it is worn
below minimum thickness, or if refinishing would re­
duce thickness below the allowable minimum. Rotor
minimum thickness is usually specified on the rotor
hub, or on the outer edge of the rotor ventilated sur­
face.
ROTOR THICKNESS
VARIATION
Variations in rotor thickness will cause pedal pul­
sation, noise and shudder.
Measure rotor thickness at 6 to 12 points around
the rotor face (Fig. 31). Position the micrometer ap­
proximately 25.4 mm (1 in.) from the rotor outer cir­
cumference for each measurement.
Thickness should not vary by more than 0.025 mm
(0.001 in.) from point-to-point on the rotor. Refinish
or replace the rotor if necessary.
Fig. 31 Measuring Rotor Thickness Variation
Checking Rotor Lateral Runout
Check rotor lateral runout if constant pedal pulsa­
tion or an occasional low pedal condition was experi­
enced. Excessive lateral runout will cause pedal
pulsation, uneven wear of the brakeshoes, and brake-
shoe knockback. Measure runout with a dial indica­
tor (Fig.
32).
Check runout with Dial Indicator
C-3339
(Fig.
32).
Position the indicator plunger at least 25.4 mm ( 1
in.) inward from the outer edge of the rotor. On
2-wheel drive models, be sure wheel bearing
end play is reduced to zero before checking
runout.
Maximum allowable lateral runout is 0.127 mm
(0.005 in.).
mOTOm
MEFINISHING
Rotor braking surfaces can be refinished by sand­
ing and/or machining in a disc brake lathe (Fig. 33).
The lathe must be capable of machining both rotor
surfaces simultaneously with dual cutter heads.
Equipment capable of machining only one side at a
time will produce a tapered rotor.